This invention relates to gun ammunition, and specifically to gun ammunition in which a round of the ammunition includes a casing which houses gunpowder and a projectile. More specifically, the present invention relates to multi-component projectiles for gun ammunition.
In all gun ammunition wherein a projectile is propelled from a rifled barrel of a weapon, the projectile spins about its longitudinal axis (about its trajectory) at high speeds of rotation. Consequently, it is of major importance that the density of the projectile be uniform in any given plane taken normal to the longitudinal axis of the projectile so that the projectile does not wobble (nutate) as it is spinning to its target. Wobble of the projectile can adversely affect both the terminal ballistics of the projectile and, more importantly, the accuracy of delivery of the projectile to the target. Severe non-uniformity of the density distribution of the projectile about its longitudinal axis can result in jamming of the projectile within the gun barrel, or in less serious wobble, damage to the lands of the rifling of the gun barrel. Accuracy of delivery of the projectile to a target also dictates that the projectile be of consistent construction, including weight, from projectile to projectile so that a consistent given load of gun powder employed in each round of ammunition will ensure that each round of ammunition functions precisely like each other round of the ammunition. In certain situations, such as sniper fire, it is imperative that the shooter be confident that each round of ammunition will perform precisely like every other round of ammunition for a given weapon for the reason, among others, that the sniper commonly can only get off a single shot to his target. This same situation exists in sport hunting and in competitive shooting.
Of relatively recent vintage is a gun ammunition projectile which is fabricated from two or more metal powders. Commonly, the metal powders are die-pressed into a cylindrical geometry. Such pressed compacts are at times referred to as xe2x80x9ccoresxe2x80x9d. To form a projectile, a core is placed in a hollow cup-shaped metal jacket having one end thereof closed and its opposite end open for the receipt of the core. After the core has been placed in the jacket and seated against the closed end of jacket, the open end of the jacket, and that end of the core adjacent the open end of the jacket, are die-formed into an ogive. The formation of the ogive tends to partially crush that portion of the core which is involved in the formation of the ogive, generating unbonded metal powder adjacent the leading end of the projectile. In those projectiles where the ogive end of the projectile is not fully closed, this unbonded powder is free to escape from the projectile during handling of a round of ammunition, while the round is in a gun, and/or after the round has been fired and the projectile is traveling to a target. Whereas the quantity of unbonded metal powder adjacent the open end of the jacket will vary from a few particulates of metal powder to many particulates of metal powder, it is to be noted that even one loose metal particle escaping from the jacket can adversely affect the operation of the gas-operated bolt actuation mechanism of an automatic or semi-automatic weapon, or can create undue localized wear of the bore of a weapon, whether the weapon be a bolt action-type weapon or an automatic or semi-automatic weapon. Further, dislocation of a material quantity of metal powder particulates can adversely affect the spin stability of a powder-based projectile, hence adversely affect the accuracy of delivery of the projectile to an intended target.
In U.S. Pat. No. 5,789,698, the present inventor disclosed the use of a solid metal cap to be placed within the jacket adjacent the exposed end of the core prior to formation of the ogive. As the ogive is formed, this cap is also deformed and urged toward the open end of the jacket where it remains lodged in position to prevent the escape of metal powder from the ogive end of the projectile. In many applications, the formation of the ogive does not fully close the open end of the jacket, commonly for purposes related to the disintegration of the projectile upon striking its target.
Whereas solid metal caps are effective for their intended purpose, their cost of manufacture and/or other disadvantages have raised the need for a different cap. One such cap conceived by the present inventor is disclosed in copending U.S. patent application Ser. No. 09/491,257, filed Jan. 26, 2000, entitled: Powder-based Disc for Gun Ammunition Having a Projectile Which Includes a Frangible Powder-based Core Disposed Within a Metallic Jacket. The cap of this copending application comprises a metal powder, particularly a tin metal powder, which is die formed into a disc of a preselected diameter, and which is of uniform cross-sectional thickness, is uniform in density throughout the disc, and which is deformable when deployed in a projectile jacket with a core and the open (leading) end of the combination is die-formed to define an ogive on the leading end of the multi-component projectile.
In accordance with one aspect of the present invention, the inventor has discovered a frangible disc useful in small-bore gun ammunition (50 caliber or smaller) including a central region thereof formed of a compressed unbonded quantity of particles of at least one metal powder and an outer peripheral skin defined by melded ones of said at least one metal powder particles. The disc is formed from a compressed metal powder compact which is heat treated under controlled conditions such that, without materially altering the dimensional aspects of the disc, the outer peripheral margin of the disc is converted into a solid skin. This heat treated disc is employed in the usual manner in a multi-component projectile for gun ammunition.
One embodiment of a method for the formation of the skin-bearing powder-based disc comprises the steps of compacting, in a die cavity, a quantity of a metal powder into a self-supporting disc, heating this disc to a temperature and for a time whereupon only the powder particles disposed on the outer surface of the disc meld together to define a skin on the outer surface of the disc, but not to a temperature nor for a time whereupon sufficient quantities of powder particles become sufficiently fluid to overcome the surface tension of the melded particles and resultant deleterious deformation of the overall original geometry of the disc.